The number and variety of medical methods available to treat cardiovascular disease has increased rapidly in recent years. More particularly, alternatives to open heart surgery and cardiovascular by-pass surgery have been extensively investigated, resulting in less invasive procedures such as percutaneous transluminal coronary angioplasty, laser angioplasty, and atherectomy. These procedures are primarily directed toward the reduction of stenoses within the vasculature of a patient by either expanding the lumen through the use of a balloon, or otherwise removing the material making up the stenosis.
While these procedures have shown considerable promise, many patients still require by-pass surgery due to the presence of extremely diffuse stenotic lesions, the presence of total occlusions and the presence of stenotic lesions in extremely tortuous vessels. Also, some patients are too infirm to successfully undergo the rigors of by-pass surgery, and because the above treatments may require surgical intervention if complications develop, these patients are untreatable.
One alternative to these procedures is known as transmyocardial revascularization (TMR). In TMR, channels are formed in the ventricle wall with a laser or other type of ablation device. These channels provide blood flow to ischemic heart muscle. A history and description of this method is presented by Dr. M. Mirhoseini and M. Cayton in "Lasers in Cardiothoracic Surgery" in Lasers In General Surgery (Williams and Wilkins; 1989 (pp. 216-223).
In the procedure described therein, after surgically opening the patient's chest to expose the heart, a carbon dioxide laser is used via an articulated arm delivery device to produce channels in the ventricle from the epicardium through to the myocardium. External pressure is used on the outside of the heart to stop bleeding from the ventricle through the newly created channel. Other early disclosures of this procedure are found in an article by Okada et al. in Kobe J. Med. Sci. 32, 151-161, October 1986 and U.S. Pat. No. 4,658,817 (Hardy). These early references describe intraoperative revascularization procedures which require an opening in the chest wall and include formation of the channels through the heart wall.
A proposed improvement in the design is described in Hardy--U.S. Pat. No. 4,658,817. A needle is added to the distal tip of the articulated arm system, with laser energy passing through the lumen of the needle. The metal tip of needle of the device is used to pierce the myocardium and the laser beam is used to create the desired channel through the remaining portion of the myocardium and through the adjacent endocardium. For a variety of reasons, the system of Hardy has not been used clinically to any significant extent. These prior procedures required the chest wall be opened in order to access the heart muscle with laser devices, which was highly invasive and resulted in severe complications.
A further improvement to the intraoperative TMR procedure is described in Aita--U.S. Pat. No. 5,554,152, issued Sep. 10, 1996, which is hereby incorporated by reference in its entirety wherein an elongated flexible lasing apparatus is inserted into the chest cavity of a patient and lasing channels are then formed in the heart wall. While the system of Aita has been found to be clinically quite successful, the system did not allow for easy access to the entire heart and was not always suitable for minimally invasive procedures through the chest wall.
What has been needed is a tissue ablation device with a probe that has the proper shape and configuration and sufficient maneuverability to access the desired areas of a patient's heart, particularly in minimally invasive procedures. The present invention satisfies these and other needs.